The present invention relates to a machine for processing elongate strand-form material comprising a rotatably mounted rotor bow. The invention furthermore relates to a method for manufacturing such a rotor bow.
Machines having a rotatably mounted rotor bow for processing elongate strand-form material are known from the prior art. Such machines are used to process leads, wires, threads or strings into cables or ropes and are called cording or stranding machines, generally differentiated between single-twist and double-twist machines. Although the invention will be described in the following using the example of a double-twist stranding machine, it is noted that the invention also relates to all other types of machines using a rotor bow of the described type.
All known embodiments of double-twist stranding machines concur to the extent that the elongate strand-form material is guided over a rotor or stranding bow, that two strand points are provided and twice as many strand twists are produced as rotor bow revolutions. Reference is made in this regard to EP 1 441 063 A1 and WO 95/04185.
The operational principle of the described double-twist stranding machines provides for the rotor bow to rotate about an axis. Double-twist stranding machines are used predominantly for manufacturing mass-produced goods such as electrical cable for the automobile industry, for example, and therefore have an accordingly very high processing speed coupled with a high rotational speed of the rotor bow, amounting to several thousand revolutions per minute.
Double-twist stranding machines are often integrated into production lines; i.e. so-called in-line production. In this type of processing, production steps upstream and downstream of the double-twist stranding machine are necessary in manufacturing the end product. In the manufacture of electrical cable, insulating the cable is for example downstream of stranding. If just one element of the production chain fails, the entire production line comes to a halt and high downtime costs ensue. Hence, formidable demands are placed on a double-twist stranding machine's functional reliability.
Rotatably mounted rotor bows often consisting of a high-strength metallic material have to date been used in double-twist stranding machines, as have rotor bows designed as very complex hollow body profiles as disclosed for example in U.S. 2006/0196163 A1.